Solid Source ('radiogenic Isotope') Mass Spectrometry
Several of the isotope systems involved in radiometric dating depend on IRMS using thermal ionization of a solid sample loaded into the source of the mass spectrometer (hence thermal ionization mass spectrometry, TIMS). These methods include rubidium-strontium dating, uranium-lead dating, lead-lead dating and samarium-neodymium dating.
When these isotope ratios are measured by TIMS, mass-dependent fractionation occurs as species are emitted by the hot filament. Fractionation occurs due to the excitation of the sample and therefore must be corrected for accurate measurement of the isotope ratio.
There are several advantages of the TIMS method. It has a simple design, is less expensive than other mass spectrometers, and produces stable ion emissions. It requires a stable power supply, and is suitable for species with a low ionization potential, such as Strontium (Sr), and Lead (Pb).
The disadvantages of this method stem from the maximum temperature achieved in thermal ionization. The hot filament reaches a temperature of less than 2500 degrees Celsius, leading to the inability to create atomic ions of species with a high ionization potential, such as Osmium (Os), and Tungsten (Hf-W). Although the TIMS method can create molecular ions instead in this case, species with high ionization potential can be analyzed more effectively with MC-ICP-MS.
Read more about this topic: Isotope-ratio Mass Spectrometry
Famous quotes containing the words solid, source and/or mass:
“Self-pity comes so naturally to all of us, that the most solid happiness can be shaken by the compassion of a fool.”
—André Maurois (1885–1967)
“Life has no other discipline to impose, if we would but realize it, than to accept life unquestioningly. Everything we shut our eyes to, everything we run away from, everything we deny, denigrate or despise, serves to defeat us in the end. What seems nasty, painful, evil, can become a source of beauty, joy and strength, if faced with an open mind. Every moment is a golden one for him who has the vision to recognize it as such.”
—Henry Miller (1891–1980)
“... the mass migrations now habitual in our nation are disastrous to the family and to the formation of individual character. It is impossible to create a stable society if something like a third of our people are constantly moving about. We cannot grow fine human beings, any more than we can grow fine trees, if they are constantly torn up by the roots and transplanted ...”
—Agnes E. Meyer (1887–1970)